Technical Field
The present disclosure relates to a display apparatus. More particularly, the present disclosure relates to a reflective display apparatus and a front light module thereof.
Description of Related Art
A color display technique of a color e-book reader employs a color filter on a reflective display panel. The reflective display panel includes a plurality of microcapsules. The color filter includes a plurality of sub-pixel zones having different colors, such as red, green and blue. A color image of the color e-book reader can be rendered by controlling grayscale variation of the microcapsules underlying different sub-pixel zones.
Generally, ambient light is essential for the reflective display panel to render the image because the reflective display panel itself doe not emit light. If the reflective display panel is operated under a surrounding of weaker ambient light, the reflective display panel cannot clearly render the image. In order to address this issue, a front light module can be disposed in front of the display surface of the reflective display panel, so as to provide sufficient light to the reflective display panel when the ambient light is weak, and to benefit the image rendering.
However, when the front light module is employed in the color e-book reader, the unduly great incident angle of the incident light to the reflective display panel may cause inappropriate color rendering. Specifically, shown in FIG. 1 is an optical path schematic view of a typical color e-book reader 900. The color e-book reader 900 includes a reflective display panel 910, a color filter 920 and a front light module 930. The color filter 920 is located between the reflective display panel 910 and the front light module 930. The color filter 920 includes light filter zones 921, 922 and 923. The light filter zones 921, 922 and 923 have different permissible wavelength ranges. The front light module 930 includes a light source 931 and a light guide plate 932. In operation, light generated by the light source 931 can travel into the light guide plate 932 through a lateral surface of the light guide plate 932, and can travel out of the light guide plate 932 through a bottom surface of the light guide plate 932, and then, the light can travel through the color filter 920 and can be reflected by the reflective display panel 910.
In detail, the light S1 traveling out of the bottom surface of the light guide plate 932 can pass through the color filter 920 and arrive at the reflective display panel 910. The reflective display panel 910 can reflect the light S1 as the light S2. The light S2 can pass through the color filter 920 and travel out of the e-book reader 900 through an upper surface of the light guide plate 932. When the light outgoing angle ϕ is unduly great, the light S1 and S2 may respectively travel through different light filter zones 922 and 923, thereby causing incorrect or inappropriate color rendering. Moreover, FIG. 2 illustrates a relation between the light outgoing angle and the light intensity of the typical front light module. It is observed that, in the typical front light module, a light outgoing angle of most light is 83 degrees, and such a great light outgoing angle tends to cause the incorrect or inappropriate color rendering.